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Old 06-19-2009, 06:51 PM   #10 (permalink)
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Originally Posted by Southcross View Post
the drawback with Autotransmission-"coasting" (not sure if that is the case any more...) is that the hydraulic pumps only work with the car in drive. Coasting in neutral, the tranny fluid isn't being circulated/cooled and the tranny overheats/burns up.
This has never been true, to my knowledge. Back in the day, you could "pop start" an engine w/ an automatic transmission because they still used rear (tailshaft) fluid pumps, but not so much anymore, unless they're designed with that purpose in mind (industrial apps, "other" designs).

When you're coasting in neutral, the engine is still running. Since the pump is driven off the engine's output (transmission input shaft), the pump is still being driven as long as the engine is turning. Putting the transmission in neutral does nothing more than bypass the valve that allows fluid pressure to build up enough to engage the clutches in the gear set, but the fluid is still flowing very much so.

Where the problem comes in is when attempting EOC with an automatic, because then the engine isn't turning, so the transmission fluid isn't being pumped, except in circumstances where the transmission is designed to be towed for long distances in neutral w/ the engine off (most or all Saturns are built this way.)
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